A generic fan is known from DE 20 2005 012 569 U1. It comprises a housing in which a pressure chamber and a suction chamber are formed, which are open to each other via a connecting opening. Furthermore, an impeller is provided which has an axial suction side arranged in the connecting opening and a radial pressure side arranged in the pressure chamber. Furthermore, an inlet for supplying a gas flow to the suction chamber and an outlet for discharging the gas flow from the pressure chamber are formed in the housing. In the known fan, the impeller is also arranged eccentrically in the pressure chamber so that the pressure chamber is configured as a spiral outside the pressure side of the impeller. Furthermore, the pressure chamber transforms tangentially into the outlet. Finally, a fan tongue is formed on the housing between the pressure chamber and the outlet.
During operation of the fan, the impeller draws in gas from the suction chamber and delivers it to the pressure chamber. This creates a gas flow. This gas flow may lead to acoustic interactions between the impeller and the fan components exposed to the gas flow. In particular, undesirable noise may be generated. The design of the fan tongue allows a significant reduction in the noise development. It has however been found that even simple changes to the fan affect the guidance of the gas flow in the fan, and thus in particular influence the noise development. So even minor modifications to the fan may require a complex revision of the fan tongue in order to bring the noise development back to a tolerable level. There is therefore a need for additional sound reduction measures in order for example to simplify an adaptation of the fan to varying installation situations.
It is known from the above-mentioned DE 20 2005 012 569 U1 to create a surround for the connecting opening from a sound-absorbing material. Furthermore, a wall opposite the connecting opening may be made of sound-absorbing material. Also, a wall surrounding the pressure chamber in the peripheral direction may be made of a sound-absorbing material. The implementation of these sound-insulating measures is however comparatively complex. Also, these measures are only effective in the higher frequency range of the disruptive noise. In order to reduce the disruptive noise in the low frequency range too, it is still necessary to modify the fan tongue.
A further sound-damped fan is known for example from DE 41 15 171 C2, in which the pressure chamber is separated by perforated walls from absorption chambers in which a sound-deadening medium is arranged.